Influence of Process Parameters on Shape Fidelity in Extrusion-Based Bioprinting: A Rheological Perspective

Extrusion-based bioprinting is one of the most accessible and versatile additive manufacturing techniques for bioengineering applications, enabling the controlled deposition of a wide range of materials, including hydrogels. These soft and viscoelastic materials, composed of polymeric chains connected by physical or chemical bonds, are crucial in ensuring cell viability and proliferation, because of their ability in absorbing significant amounts of liquid. In this context, shape fidelity, defined as the degree of correspondence between the printed construct and its digital model, emerges as a critical performance metric. This study investigates the influence of key process parameters, i.e. inlet pressure, printing speed and bio-ink temperature, on shape fidelity in the extrusion bioprinting of two hydrogels: a natural alginate/cellulose blend and a synthetic polyethylene glycol-based material. Comprehensive rheological characterization, including oscillatory tests and flow curves, was performed to assess the materials’ viscoelastic behavior and shear-thinning properties. A shape fidelity index (SFI) was introduced and applied to quantify dimensional accuracy across 24 different parameter configurations. The resulting construct quality revealed clear correlations between process conditions and material rheology. The synthetic hydrogel exhibited greater stability under varying process conditions, making it easier to achieve high SFI values. In contrast, the natural hydrogel was more sensitive to the applied process parameters, showing notable instability. Nevertheless, when optimized input variables are used, the natural hydrogel can attain even higher SFI values. These findings underscore the importance of integrated rheological analysis and parameter optimization for advancing bioprinting performance and improving the fabrication of complex and high-resolution biomedical structures.